Atmospheric pressure falls rapidly as the center of the hurri- 

 cane approaches and as the velocity of the wind increases, lliniraim 

 barometric readings do not always occur in the center of the eye. 

 In some instances, the ninimura is reached at the beginning of the 

 calm period while in others the miniinum is reached at the end of 

 the calm period. Usually the barometric low is about tiro inches 

 below the normal sea level pressure of 30 inches. However, in 

 several hurricanes pressures of as much as tliree inches below 

 normal have been recorded. In the United States, the lowest baro- 

 metric pressure ever recorded was 26,35 inches at tlie northern end 

 of Long Key, Florida, on September 2, 1935« 



30. RkHWAlL 



Another characteristic of a hurricane is the heavy rainfall 

 that usually accompanies the storm. At the edge of the disturbance 

 rainfall is light, norma!l.ly in the form of shovrers. As the center 

 arroroaches, the showers increase in frequency snd intensity, be- 

 coming heavy to excessive near the eye. The heaviest rain usually 

 falls ahead of the eye, driving torrentially from spiral bands of 

 clouds that sometimes produce nearly two inches of rain per hour. 

 For a 2l4-hour period, amounts exceeding 20 inches are not vmcommon. 

 Record rainfall near the Narragansett Bay area occurred dioring 

 Hurricane Diane (Au§.:;ust 15^5) when 18,15 inches of rain fell at 

 Westfield, Ttissachusetts, on the l8th, 



31. WAVES 



Much of the Itiirricane damage is caused by xraves generated by 

 hvirricane winds. Vessels at sea suffer greatly in the northeast 

 quadrant of the hurricane and in the confused seas of the storm 

 center where waves li5 feet or more in height have been I'eported. 

 These mountainous vraves appear in wild pyrai-.iidal masses and the 

 magnitude of tlieir destructive ^cvicr is I'evealed only in the 

 appalling record of lives lost and ships sunk at sea or wreclced 

 on shoals and shores. Such gic'.nt ocean '.raves uill traverse 

 tremendous distances while diminishing in size and strength, 

 reaching distant shores one or two da3'-s in rdvance of the hurri- 

 cane and causing damage even before the onset and release of the 

 fury contained in the storm proper. 



In the deep water of the open ocean, the height, period and 

 velocity of many of the i/aves produced are a function of the vrind 

 velocity. The ulti;,iate sise of the waves cepends upon the force 

 and duration of the wine and the 'fetch or distance tlie \:ave travels. 

 As ocean waves co-ie into shoal waters, tbeir fon-.'ard novnment is 

 slowed by friction on the bottor"., and they rise to a r.ov; height 



18 



